arrow

MINOR: [R] Should build ignore __pycache__ directory (#15076)

I noticed that the `inst/__pycache__` directory remains in the released R arrow package version 10.0.1.

```r
system.file("__pycache__/demo_flight_server.cpython-38.pyc", package = "arrow")
#> [1] "/usr/local/lib/R/site-library/arrow/__pycache__/demo_flight_server.cpython-38.pyc"
```


Lead-authored-by: SHIMA Tatsuya <ts1s1andn@gmail.com>
Co-authored-by: eitsupi <50911393+eitsupi@users.noreply.github.com>
Co-authored-by: Jacob Wujciak-Jens <jacob@wujciak.de>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>